1. Electrical Power System
March 13, 2004

2. Introduction The DINO power system is a direct energy transfer system
It will contain a main battery composed of 4 lithium-ion polymer cells with a nominal voltage of 15V +/- 3V
It will contain a 28V battery dedicated to the deployment experiments
Power generation shall be provided by the Flexible Integrated Thin-films solar array (FITS)
A secondary solar array shall be mounted on the panels of the structure
The EPS shall provide voltages of 5, +/- 12 and 28V
Colorado Space Grant
Consortium

3. Electrical Power System Description
Direct energy transfer system
Single Solar-Array technologies
Conventional body-mount crystalline cells
Thin-Film (FITS) Flexible Array
System will switch solar array strings and spacecraft loads, and will require 4 switches for the FITS
Will require 16 (TBR) switches for the backup SA
4 power distribution switches capable of transferring less than 3 Amps
12 power distribution switches capable of transferring less than 1 Amp
System will use 4 A-hr Lithium Polymer cells at 3.7 Volts for power storage
4 Cells will be in series, for a 15V +/- 2V, 4 Ahr battery assembly
Battery charging will be accomplished using several charging modes:
Nominal sub-capacity charging; entire stack is charged to 95% capacity
This will be the default mode
Full-charge; entire stack charged to 100% capacity
Cell conditioning over-charge; as stack ages, it will lose capacity, which can be restored by judicious over-charging
Temperature and voltage monitoring will be the primary means of controlling battery
Colorado Space Grant
Consortium

4. Dino EPS Block Diagram
Colorado Space Grant
Consortium

5. Changes Since PDR
The EPS board will be designed by CSGC and have industries review the design instead of procuring an off the shelf card
The 28V supply will deploy 2 frangibolts, 1 set of memory hinges, lightband, the HOPS and the boom
Power supply outputs shall have inhibits
The EPS card will communicate with C&DH through a RS-422 serial line
A PIC and an A/D converter will replace the FPGA
Monitors will be placed on the essential components (voltage busses, battery and solar arrays) instead of all switches
Power shall have a watchdog to reset C&DH
Colorado Space Grant
Consortium

6. Functional Requirements
Compliance
The EPS shall confirm the status of the inhibits at all times
The EGSE and umbilical cord shall confirm the inhibits status. Continuity loops will establish current status and C&DH will indicate inhibits state.
The main battery shall last the duration of the mission life of a required 6 months and mission goal of 12 months
The battery shall be oversize by 20% using maximum values of all devices. The battery shall be charged every 3 cycles and overcharged periodically to recover capacity lost.
28V supply shall deploy all mechanisms
The battery shall be sized to 120% of the needed power and shall be tested with all deploy mechanisms.
Colorado Space Grant
Consortium

7. Functional Requirements
Compliance
The 5V power supply shall power all devices using 5V
The supply shall be rated to double of the needed watts based on the power profile.
The 12V power supply shall provide the needed power to the systems require 12V. The supply must also have positive and negative voltages
The supply shall be rated to double of the needed watts base on the power profile. The supply chosen will be capable of using negative voltages and positive voltages
The charge controller shall be capable of charging the main battery to specified ranges.
The charge controller shall use a comparator to ensure the battery will remain charging until it is within a desired range
The EPS card shall contain a watchdog to reset C&DH
If contact with C&DH can not be established for a period of 10 minutes power to the C&DH will be turn on then off. Time will be kept using a PIC.
Colorado Space Grant
Consortium

8. Functional Requirements
Compliance
EPS shall send health and status to C&DH
Once the monitors return values it will be processed by the A/D converter and the micro controller will send it onto C&DH.
EPS shall receive commands from C&DH to turn on devices and systems
Commands will be sent through a serial line to a micro controller. The micro controller will send the appropriate analog command to turn on and off switches.
Power Generation
The EPS system shall receive power from the primary FITS solar array. Power will also be generated by body mounted solar cells.
Storage of power
Power shall be stored in the main battery. Charging of the main battery shall occur once every 3 cycles.
Distribute Power
Power shall be distributed through power lines of 5, +/- 12 and 28V. C&DH shall instruct the EPS system to close switches to give power to subsystems.
Colorado Space Grant
Consortium

9. CURRENT BEST ESTIMATE = 10 A
DINO EPS Compliance with Requirements
PMAD card fits within 10”x10” square on other side of Zenith Plate
System masses less than 2.25kg
PMAD – .75kg
Cells – ~.1kg/each; .4kg
FCC – ~.1kg
Monitors – ~.1kg
Potting/misc – TBD
EPS system shall not heat spacecraft unduely
Cells use a battery radiator
PMAD TBD
Colorado Space Grant
Consortium

10. EPS Battery Safety Requirements Compliance and How Addressed
Requirement Met?
How Addressed
Un-powered bus in ICU
Main Battery – NO
28V Battery – NO
Solar Arrays – YES
Inhibits/Battery Design
Inhibits
3-fault tolerant battery inhibits
YES
Latching Relays
Protection vs Electrolyte leak
Potting/absorbent materials, 28V vent orientation
Blocking Diodes on all cells in series
Charge Control design/test
28V Battery – testing
Blocking Diodes on parallel cell strings
28V Battery – TBD
TBD
Overcharge/discharge protection
Voltage monitoring of battery
Cell temp shall not exceed 40°C
Thermal design/test
Internal Short protection
Main Battery – YES
28V Battery – YES
Potting physically isolates cells
Fuses on each string
Cells shall not be damaged by launch
Potting/Case design
Colorado Space Grant
Consortium

11. EPS Battery Safety Requirements Compliance and How Addressed
Requirement Met?
How Addressed
Cells shall not be damaged by thermal cycling
YES
Thermal design/test
Cells shall be either UL-certified or undergo a flight qualification
Main Battery – TBD
28V Battery – Yes
TBD
UL-certified
Cells shall not heat excessively during operation
Testing
Cell/PMAD Monitors change indicate monitor failure
PMAD – TBD
28V Battery – TBD
Power feeds using separate lines with a common start and end point shall contain a protective device on each feed
Main Battery – NO
Flat Conductor Cable – NO
Colorado Space Grant
Consortium

12. EPS Circuit Protection Safety Reqs – Compliance and How Addressed
Safety Requirement
Requirement Met?
How Addressed
Small, sub-mini, & cartridge fuses shall be derated 50%
Yes
Design/part selection
Shall use a minimum of 1MΩ resistance between DINO and orbiter ground plane
YES
Design
Connector Shells shall have <2.5mΩ resistance to DINO ground
Design/test
Connector pin-to-pin resistance shall not exceed 50mΩ
Connector selection/testing
EGSE shall have a minimum of 1MΩ resistance to DINO
TBD
Parallel power feeds require individual circuit protection
Colorado Space Grant
Consortium

13. EPS Monitors/Verification Requirements Compliance and How Addressed
Safety Requirement
Requirement Met?
How Addressed
No hazardous events shall occur until DINO is clear of the Shuttle
YES
ICU sep switches activate a C&DH timer
Processes controlling hazards shall be monitored
Deployment – YES
Radios – NO/TBD
Inhibits
Un-powered initially
Monitoring at launch site shall be provided if needed
EGSE Design
Colorado Space Grant
Consortium

14. Manufacturing/Test Facility Requirements
Manufacturing Facilities:
Machining of zenith plate – ITLL machine shop
Main Battery assembly & potting – BATC facilities/assistance
28V Battery assembly & potting – CSGC shop
PCBs – manufactured with Broad Reach assistance/facilities
Covers/mounting hardware – provided by DINO structures team
Test Facilities:
Thermal-vacuum chamber for system testing – BATC
Test battery performance in a vacuum
DINO testing with realistic thermal conditions
Shaker table for 20g sine-burst testing – BATC
Breakout boxes for EGSE – CSGC/BATC
18 pins for Main Battery
TBD pins for subsystem switch monitors
TBD pins for C&DH
Colorado Space Grant
Consortium

15. Power Card Schematic
Colorado Space Grant
Consortium

16. Power Card Power Distribution 24 power distribution switches
Power Processing
Three power supplies (5V, 12V and 3.3V)
Communication with flight computer
RS-485
Power Management
Uses PWM current control technique to transfer the power from the solar array to rest of the spacecraft
Safety
Provides safety inhibits according to NASA Safety Requirements discussed above
Colorado Space Grant
Consortium

17. DINO Battery Schematic
Colorado Space Grant
Consortium

18. Battery Description The battery chemistry is Lithium-Ion polymer
The cells are in a prismatic configuration
The main battery shall contain 4 lithium-ion polymer cells connected in series
The cells have a nominal voltage of 3.7V and a
capacity of 4 Ahr
The battery shall last for 2000 charge/discharge cycles
Cell dimension are 4” X 4”
Colorado Space Grant
Consortium

19. Battery Size Analysis
Colorado Space Grant
Consortium

20. Primary 28V Deployment Battery Description
28V battery system shall consist of cell strings of 3 9V cells, connected in parallel
System shall use either 3 strings of Alkaline 9V or TBD strings of Lithium 9V cells
System shall provide power to – What devices?
Battery shall be contained within an anodized aluminum case
Cell strings kept physically isolated
Cell contacts and interconnects shall be potted over to form 1 part
Absorbent material shall be used in the case to soak up leaked electrolyte
Case vents shall be oriented upward during launch (location in DINO TBD)
Fuses shall be provided on the individual strings, as well as the battery ground
System has been tested and proven w/ Alkaline 9V cells
Lithium cells have not been tested yet
Positive
Battery Assembly
3 Cell String
Negative
Colorado Space Grant
Consortium

21. Deployment Battery Case
1/8” anodized Aluminum
3-cell string
Cell string well
String interconnects
on outside of case
Case interfaces with
DINO isogrid
Colorado Space Grant
Consortium

22. Analysis and Prototyping Reports
28V power system:
Load testing shows that 9 Alkaline 9V cells provide sufficient power
Alternate design using 6 Lithium 9V cells is under development
A battery short test using a stack of 9 Alkaline cells produced the
following:
- Cell bottoms swelled, and in some cases, ruptured
- Electrolyte material ejected from cell cans
- Battery internal temperatures reached 85°C
Colorado Space Grant
Consortium

23. Solar Array Analysis
Colorado Space Grant
Consortium

24. Solar Array Electrical Properties
Beginning of Life
End of Life
25° Celsius
78° Celsius – Radiation Degradation
Area
1.10
Voltage – String
24 Volts
19 Volts
Current – String
1.4 Amps
1.27 Amps
Power – Total Watts
110 Watts
90 Watts
Array Efficiency 8%
4.60%
Colorado Space Grant
Consortium

25. Plans for Support Equipment
To emulate the C&DH commands to the EPS system, Flight software shall be used to control switches and charge commands
Flight software shall be connected through an RS-422 serial line
Outputs shall be verified using multi-meters, oscilloscopes and break out boxes
Thermistors, voltage and current sensors shall have a testing harness to record the data and inspected
Power supplies shall mimic the input power from the solar arrays
Minimized custom
Colorado Space Grant
Consortium

26. Document Tree
Colorado Space Grant
Consortium

27. Status and Plan of Action
Documentation
Document
Status and Plan of Action
Technical Manual
60% complete, once the system design is completed and components are chosen a description of how the components work will be written up
System Description
Completed
Performance Test
Outline completed
Functional Test
Outline completed, CSGC will determine acceptable parameters of operation
Environmental Test
20% complete, initial outline for environmental testing has been written.
28V Test
80% complete, CSGC needs to test another set of batteries and make a final decision on the cells that will be used in flight
Colorado Space Grant
Consortium

28. Status and Plan of Action
Documentation
Documents
Status and Plan of Action
Electromagnetic Interference Test
20% complete, an initial outline has been written up. To complete this document we must choose all of our components and determine the amount of exposure the system will encounter.
Mechanical Schematics
80% complete, the mechanical design requires a definite size of the battery cells and refinement on interfaces
Electrical Schematics
50% complete, CSGC needs to obtain software to compile an entire system schematic
Colorado Space Grant
Consortium

29. Issues and Concerns
Starting up the spacecraft when leaving the shuttle (initial power-up)
Monitoring inhibits and sensors via GSE with no internal power provided
Watchdog timing circuit and an inhibit between Power and C&DH
Colorado Space Grant
Consortium

30. Current EPS Status Electrical Design 70% complete
Mechanical Design 90% complete
Safety designs 70% complete
EPS card on track for summer prototyping and testing
Colorado Space Grant
Consortium